Table of Contents

 

See also the “Climate Change and global warming” chapter in the Issues section.

1. Overview

South Africa is a relatively dry country. The climate varies from desert to semi-desert in the west, to relatively wet in the eastern parts adjacent to the Indian Ocean. Compared to the rest of the world, this country has a very low average rainfall – 470mm per year, which is only half of the world average.

South Africa’s rainfall is typically unreliable and unpredictable. South Africa is periodically afflicted by drastic and prolonged droughts, which often end in severe floods. There are several explanations for the variable rainfall. One reason is related to the oceans around the country. Another is linked to our position in the global weather and climate systems. For example, we receive some rainfall from warm, moist air that sweeps down over the country from the North- West. In the South Western parts of the country, cold fronts usually bring winter rainfall. La Niña and El Niño also influence our rainfall from time to time (at the time of finalising this chapter the country has suffered enormously from a severe drought caused by El Niño).

Because of the topography as well as the rainfall distribution, 60% of South Africa’s run-off water is in rivers that flow through only 20% of the country (the eastern region). Most of our clouds are caught up by the Drakensberg mountain range in the east where precipitation occurs. This water then runs down the steep side of the Drakensberg and into rivers of KwaZulu-Natal and into the sea.

On average, only some 9% of rainfall reaches the rivers.

The country falls squarely within the subtropical belt of high pressure, making it dry, with an abundance of sunshine.

Weather

  • Weather is the condition of the atmosphere at a specific time, or over a very short period of time, at a place.
  • It is described by various observed meteorological phenomena and measured elements (including atmospheric pressure, temperature, humidity, precipitation, cloudiness and wind speed as well as wind direction).

Many day-to-day decisions of farmers depend on current weather conditions and how it will change over the next few days, weeks or months.

Climate

  • The average condition of the atmosphere at a place or in a region as observed over a period of at least 30 years.
  • This average condition, or the climate, is usually described in terms of temperature, precipitation and wind.

The climate of a place will determine what crops will succeed best in a specific region, or what animals will best suit a specific region.

Agrometeorology

Agrometeorology studies the influence of climate and weather on agricultural production. As South Africa’s seasonal climate is highly variable and precarious, climate is a deciding factor in successful agricultural production.

 

 

2. Lightning

SA is a severe lightning risk area, with one of the highest rates of lightning strikes per square kilometre in the world. Lightning poses a hazard to people and livestock, and can cause expensive damage to infrastructure. Every year, there are reportedly up to 100 lightning-related fatalities per year (and probably four to five times as many survivors requiring treatment).

According to the data collected thus far collected by the South African Weather Service, the most dangerous place to live in terms of lightning is the windward slope of the northern Drakensberg. The northern Drakensberg’s “flash density” of 15/km² extends into northern KwaZulu-Natal and the Mpumalanga lowveld.

The data collected from the network are used to form lightning-risk maps. These range from a map of average lightning flashes per municipality and a lightning intensity-risk map to a “positive lightning” risk map. These may be found at www.weathersa.co.za/observations/lightning.

The data collected from the network are used to form lightning-risk maps. These range from a map of average lightning flashes per municipality and a lightning intensity-risk map to a “positive lightning” risk map.

Source: “Calculating the deadly statistics of lightning strikes”, an article in Business Day, 19 March 2012; a paper by Innopro at www.innopro.co.za/uploads/innopro-ID392-ISMcKechnie-IRJandrell-ICLP2014.pdf